Noise and power optimization of a MMIC quasi-circulator

This paper first sums up the power and noise limits of various types of active circulators and quasi-circulators. It then presents the design and measured performances of a narrow-band quasi-circulator module tailored for use in a transmit/receive (T/R) module. Its design implements an active power divider and a combiner. A method to calculate the minimum noise figure is presented for this circuit. At 4 GHz the device demonstrates a noise figure of 5.5 dB and an output power of 18 dBm with associated gains of 4 and 7.6 dB for the receive and transmit path respectively. The third-order intercept point (IP3) is equal to 25.6 dBm for the transmit path.